Uses git checkout 38726e67340b2b60715fa2f342dc800273d3772f -- . Remove unused patches from distgit.
https://downloads.isc.org/isc/bind9/9.16.11/RELEASE-NOTES-bind-9.16.11.html
Include verification on build time, with link to GPG keys on upstream site. Signed-off-by: Petr Menšík <pemensik@redhat.com>